90% of the births I attend are more than 45 minutes from a hospital, and it has never been a problem. Even when we had a cord prolapse. So I am not personally worried about it, it's the only option for most people. However, I know people who haven't had one because of the distance. In all my years of trying to find out more about birth centers, that would be one of the major stumbling blocks around here, it would have to be very close to the hospital, and when they tried that about 20 years ago, the doctors had it shut down pretty quickly.
I live in a rural area though and everyone is used to having to drive for EVERYTHING. In their minds, if their is an emergency it's no different then if there is an emergency at the farm, or shop, or whatever, or even a car accident, they would have to be driven or airlifted quite a distance. That's just a price that is paid for living in a rural area.